1. Field of the Invention
The present invention relates to a dressing apparatus, which is capable of removing a pair of electrode tips from a welding gun for replacement as well as grinding a pair of electrode tips mounted on a welding gun for better spot welding.
2. Description of the Prior Art
Hitherto, the grinding of the electrode tips of a welding gun has been carried out in such a way that the electrode tips are ground by bringing the electrode tips into contact with the cutter of a dressing apparatus for a predetermined time period, for example, 15 seconds, and the completion of grinding is verified by determining whether the front end surfaces of the electrode tips are ground to have desired shapes or not.
When the front end surfaces of the electrode tips are not sufficiently ground to have desired shapes, the electrode tips are brought again to the cutter of the dressing apparatus and ground again to have desired shapes. An electrode tip that is consumed to the extent more than a predetermined value should be replaced by a new electrode tip. In the past, the electrode tip is removed from the shank of a welding machine utilizing a tip removal apparatus, such as that shown in Korean Unexamined Patent Application No. 2000-15455.
However, the prior art tip grinding and removal operations are performed by independent apparatuses, so the cutter of a dressing apparatus and the rotary board of a removal apparatus are separately provided. In particular, the operation of automatically replacing an electrode tip is inefficient since the separate apparatuses occupy a relatively wide space, the costs of the apparatuses are high, the moving area for the electrode tip is relatively wide and teaching a welding robot is complicated.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a compact dressing apparatus which can remove a pair of electrode tips from a welding gun for replacement as well as grind a pair of electrode tips mounted on a welding gun for better spot welding.
Another object of the present invention is to provide a dressing apparatus which allows a welding robot to be easily taught when a welding operation is performed in an automated production line.
In order to accomplish the above objects, the present invention provides a welding electrode tip dressing apparatus for grinding a pair of electrode tips mounted on two opposite shanks and for removing the electrode tips when they are spent. The dressing apparatus comprises a tip grinding unit provided with a cutter so as to grind the pair of electrode tips and a tip removal unit provided with a removal mechanism so as to remove the pair of electrode tips. The tip grinding unit and the tip removal unit are adjacent each other, preferably side-by side, in an apparatus body and are connected to a drive transmission mechanism connected to and driven by a single drive device.
The drive transmission mechanism may include a plurality of speed reduction gears so that the tip grinding unit and the tip removal unit are driven slower than the drive device.
The apparatus body may be held between springs and arranged with the springs to be moved by axial movement of the electrode tips in contact with the tip grinding unit.
The tip grinding unit has a cutter, which may have an outer gear portion that engages a speed reduction gear in the drive transmission mechanism so that the cutter is driven by the drive device. The cutter has an aperture that receives a welding electrode tip and may have two back-to-back grinding surfaces for grinding two opposing electrode tips simultaneously.
The tip removal unit has a rotary board with an aperture for receiving a welding electrode tip and a plurality of claws disposed around the aperture which are made to move to selectively penetrate or release from the welding tip upon normal or reversed rotation of the rotary board about a rotation axis. Each claw is received in a radial slot in the rotary board and moves against an undercut surface or a withdrawal surface of the slot. When the claw moves against the undercut surface, the claw is pushed to an undercut position whereat the claw penetrates the welding tip when the rotary board is rotated in a first direction. When the claw moves against the withdrawal surface, the claw is pushed to a withdrawal position whereat the claw releases from the welding tip when the rotary board is rotated in a second direction.
A holding unit on the tip removal unit holds the claws, has an aperture for receiving a welding electrode tip, and has the same rotation axis as the rotary board. The holding unit rotates relative to the rotary board to move the claws in the slots.
The holding unit is selectively rotationally restrained by a combined rotation restrainer which may include a pair of brake hooks oppositely disposed about a portion of the holding unit. The brake hooks are actuated to selectively close or open to selectively restrain or release the holding unit. The brake hooks provide a restraining force on the holding unit when the brake hooks are closed, and the restraining force is set to allow rotation of the holding unit relative to the combined rotation restrainer after the claws have penetrated the welding electrode tip.
The combined rotation restrainer may include a cylinder with a piston operating therein. The piston has a piston rod constructed to release the rotation restraint of the holding unit during operation of the tip grinding unit.
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description, claims and drawings.